The invention relates to a valve assembly for use in connection with carpet cleaning extraction machines. The invention allows the mixing of different liquids in a mixing chamber, such as clean water with detergent, and the discharge of a selected liquid without the formation of a vapor lock that would inhibit the discharge of the selected liquid. In particular, the invention prevents the formation of a vapor lock when water is being drawn into a chamber that would prevent the subsequent discharge or spraying of either water or a water/detergent mixture.
Carpet cleaning machines of the extraction type are typically used to inject water or a water/detergent mixture into the carpet fibers to be cleaned. The machine then typically extracts the soiled water/detergent mixture by vacuuming, thereby extracting particulate matter and other soiling agents and contaminants from the carpet along with the water and detergent. Examples of such carpet cleaning extraction-type machines include U.S. Pat. No. 6,158,081 to Kasen et al., titled Water Extraction Cleaning Machine with Variable Solution Mixing Valve, incorporated by reference herein for all purpose. The valve of the Kaspen et al. invention allows different mixes of detergent and water to be adjusted by a knob. U.S. Pat. No. 6,073,300 to Zahuranec et al., titled Valve Assembly for Carpet Extractor, incorporated by reference herein for all purposes, is directed to a spray valve assembly for a carpet extractor which provides ease of coupling of a remote attachment for access to hard to reach areas and selective supply of cleaning solution to the attachment and the floor. Extraction cleaning machines are well known in the art, and it is submitted that the valve assembly of the present invention is particularly useful in machines of this type.
Predicate to spraying either water or a water/detergent mixture, each liquid must be drawn into a compartment from their respective holding tanks. Water is typically drawn in first, before the typically more viscous detergent. It is at this initial stage of drawing water into a chamber from a tank or reservoir that a problem frequently occurs that impedes operation of the device. The chamber that water is drawn into is usually air-filled immediately prior to the water entering from its holding tank or reservoir. As water enters the air-filled chamber, insufficient pressure is generated to force a valve (typically a shut-off plunger rod assembly) into the closed position. Consequently, an air or vapor lock forms within the chamber, thereby preventing the ultimate discharge of the liquid. The invention solves this problem by creating an air release, discharging the air in a single direction and destroying the air lock. Destroying the air lock permits the discharge of a selected liquid though a discharge outlet.
In the extraction cleaner application, the vapor lock problem is most acute where the water tank is located in the lower part of the extractor, where the water level is low and thus the gravity-induced pressure is even more likely to be insufficient to overcome the vapor lock. Thus, the invention allows a greater diversity of positions to locate the water tank, without incurring an air lock problem. This allows much greater flexibility in the design of extraction cleaners.